This invention relates to apron attitude adjustment for loading and conveying machines.
Broadly, such machines utilize a front end gathering implement to sweep rock, sand, ore or other loose material onto a self-contained conveyor for transport to a discharge location, usually disposed at the rear of the machine. An apron is disposed at the forward conveyor end, has a front end edge adapted to move forwardly along the ground with the machine and a rear end portion spaced slightly above the conveyor to deposit material thereonto. The gathering implement is normally mounted to the front portion of the machine frame, extends substantially ahead of the apron and is adapted to force material up the inclined apron.
Vehicle transport means, such as crawler treads, support the machine on the ground and may be positioned substantially behind the apron and front frame portion to move the center of gravity of the entire device rearwardly in view of the substantial weight forces at the front.
The loading and conveying machines under consideration here can be utilized in tunneling operations, although it is contemplated that they may find more extensive use above ground. In any event, they are often subject to variations in level of terrain, both during actual loading and also during transport from place to place.
In order to accommodate rough terrain, and for transport purposes, it has been found desirable to pivotally mount the conveyor intermediate its ends and also to pivotally mount the rear of the apron to the machine frame and as low as possible. Pivotal adjustment of these elements has been accomplished by suitable hydraulic cylinders and the like.
It has been found that such machines will have difficulty in traversing rough terrain in that the front components of the machine will undesirably engage a hill or rise in the ground unless the components are properly positioned.
These machines have a basic "approach angle" defined by the level ground plane and a forwardly and upwardly inclined plane tangential to the arc described by the front of the treads and extending through the lower front frame corner. Except on flat ground, the angular space defined by these two planes must be kept clear of machine elements to avoid undesirable contact with ground undulations.
When rough terrain is to be encountered, the apron can be pivoted upwardly to clear the angular upper approach plane. However, it has been discovered that although the apron pivot is disposed above the approach plane, pivotal raising of the front end of the conveyor will cause the conveyor to undesirably engage the raised apron before the conveyor can clear the plane.
In addition, during operation of the machine, it may be desirable to adjust the rear discharge height of the conveyor. This necessitates pivoting of the conveyor about its intermediate pivot axis, thus changing the clearance space or gap between the apron and conveyor. Any substantial increase in this gap will place undesirable loads on the conveyor mechanism and machine frame, in view of the substantial weight and bulk of the materials being loaded onto the machine and the relative motion of the parts.